<!DOCTYPE html>
<!--
 | If the element has "position: fixed", the containing block is established
 | by the padding edge of the nearest ancestor with a transform.
 |   https://www.w3.org/TR/CSS21/visudet.html#containing-block-details
 | NOTE: While this is not explicitly stated in the spec, which states that
 | the containing block of a fixed position element must always be the viewport
 | this is how all major browsers handle them.
 -->
<html>
<head>
  <style>
    body {
      margin: 0px;
    }
    .fixed-positioned {
      position: fixed;
    }
    .transformed {
      transform: rotate(0deg);
    }
    .level-1 {
      background-color: #b3e5fc;
      padding: 10px;
    }
    .level-2 {
      background-color: #40c4ff;
      padding: 20px;
    }
    .level-3 {
      background-color: #00b0ff;
      padding: 40px;
    }
    .level-4 {
      background-color: #0091ea;
      height: 120px;
      width: 120px;
    }
    .top {
      top: 0;
      width: 60px;
      height: 60px;
    }
    .fixed-positioned.level-4 {
      background-color: #01579b;
    }
  </style>
</head>
<body>
  <div class="fixed-positioned transformed level-1">
    <div class="fixed-positioned transformed level-2">
      <div class="level-3">
        <div class="level-4"></div>
        <div class="fixed-positioned top level-4"></div>
      </div>
    </div>
  </div>
</body>
</html>